Just use a normal hot water bottle for gentle warmth and maintain a straight posture when sitting. Simple household adjustments are the best and easiest.
Don't spend too much on expensive maternity chairs or pillows. A regular firm cushion or folded blanket behind your back works perfectly and costs nothing.
Honestly, resting with a pillow under my knees and eating some warm comfort food was my go-to. Just make sure you aren't standing for too long in the kitchen.
Since I had some complications, my doctor strictly told me to avoid any home remedies or massages. If your backache is severe, please check with your doctor first.
My mother-in-law gave me a small pillow to keep behind my back whenever I sit. She also insisted on a gentle mustard oil massage which was so relaxing.
Keep an eye on your posture now, because breastfeeding later can also strain your back. Sleeping on your side with a pillow between your knees helps align the spine.
I was already so exhausted with vomiting, and then this backache started! Using a warm water bag (not too hot) on my lower back and sleeping on my side really helped.